Electronic musical instruments



March 27, 1962 R. H. PETERSON ELECTRONIC MUSICAL INSTRUMENTS 2 Sheets-Sheet 1 Filed Sept. 15, 1958 March 27 1962 R. H. PETERSON 3,026,756

ELECTRONIC MUSICAL INSTRUMENTS Filed Sept. l5. 1958 y Zigi 2 Sheets-Sheet 2 7i 4050 g@ \\\\\\\\\\\\\\\\v 96 @Bawag/Dawson United States Patent C "ice 3,026,756 ELECTRONIC MUSICAL INSTRUMENTS Richard H. Peterson, 10108 Harnew Road E., Oaklawn, Ill. Filed Sept. 15, 1958, Ser. No. 760,924 3 Claims. (Cl. 841.01)

My invention relates to electronic musical instruments, and includes as one of its primary objectives, a multiplicity of particular details of construction and arr-angement of parts to facilitate mass production at minimum expense, combined with freedom from mechanical or electrical or acoustic defects comparable to that obtainable with the most meticulous and painstaking piece by piece fabrication and assembly'by hand.

More specifically, the completek structure of a multiplicity of independent individual oscillators can be housed in a compact space ofdrastically reduced volume, while at the same time every part of the complete instrument lis much more readily accessible for inspection, adjust-y ment, or repair, without removal. .Also-, in the rare instance when any oscillator requires removal and return for factory reconditioning, the oscillators are grouped in small groups of 6 only, and each such subordinate group constitutes a unitary sub-assembly that can be electrically disconnected by withdrawing 2 plugsand mechanically separated by unscrewing 2 mechanical fastening members, and replaced by a duplicate assembly in a few minutes by a relatively unskilled serViceman.

In manufacture, each individual oscillator involves electrical circuitry requiring approximately 42 soldered joints between metallic conductors, but onlyl 3 hand 4soldering operationsiare involved, and all the other soldered joints for 6 separate and independent oscillators can be soldered simultaneously in a single soldering operation, with each joint completed somewhat more thoroughly and permanently than can be depended on with typical individual hand-soldered unions.

The transistors employed are practically ageless with respect to their operating life.

The main capacitor of each tank circuit must be matched to its inductor coil. The most convenient mass production process is to pretune each tank circuit coil with its capacitor, and then vclip these two parts together. All the smaller capacitors and other components are in a unitarysub-assembly, put together without any electric matching procedures, and mechanically affixed to a single printed circuit board. Then the circuit board and the separate coils and main capacitors are all aiiixed to a main external panel and frame.

In the accompanying drawings:

FIGURE l is an exploded perspective of the rear side of a small, or spinet, home organ embodying the invention;

FIGURE 2 is an isometric projection of one complete sub-assembly having oscillators for sounding the note Fit in 6 different octaves;

FIGURE 3 is a face view of the under, or sheltered, side of the printed circuit embodying nearly all of the soldered connections;

FIGURE 4 is a face View, on a reduced scale, of the subass'embly of FIGURE 2, indicating its attachment to the supporting frame;

FIGURE 5 is an end view of the sub-assembly of FIG- URE 2, in the position it occupies when the operator is about to perform the operation of soldering nearly all the soldered joints of all the separate circuits;

FIGURE 6 is an enlarged detail section, -as on line 6 6 of FIGURE 3, indicating a soldered union formed with the assistance of a gripping pin, or stud;

FIGURE 7 is an enlarged section, as on line 7--7 of 3,026,756 Patented Mar. 27, 1962 FIGURE 3, indicating the formation of a soldered union without the aid of a gripping'pin;

FIGURE 8 is a top plan view as on line 8 8 of FIG- URE l, of three adjacent sub-assemblies;

FIGURE 9 is an isometric projection of a transistor and its leads;

FIGURE l0 is an isometric projection of a diode and its leads, as in section on line 10-10' of FIGURE 3; and

FIGURE 1l is van enlarged fragmentary section, as on line 11-11 of FIGURE 4, with a modified coil constluction shown in isometric projection.

Referring first to FIGURE l, the instrument ,casing 10 has a removable back panel 12. The part particularly involved in the present invention is the tone generator, made up of twelve individual sub-divisions referred to as tone-generator chassis 14. Each of these comprises a primary base support or panel 16 having a small slot 18 at. bothy ends to receive a conventional fastening bolt 20 for fasteningit to horizontal angle beams 22 in the orientation indicated in FIGURES l and 4. Supported on each panel 14 is a skeleton frame comprising end members of metal. Each end member has feet 24 affixed to the panel near its corners, as by threaded fastening members 26. From each foot a riser 2S extends perpendicular to the panel 16, and the upper ends of the risers are integral with inwardly inclined roof beams 30, which are integrally united at the apex 32. The angle between the roof beams is 60. The roof beams 3'0 on one side are affixed to the edges of a printed circuit board 34, which is supported by the beams `and which also braces the beams to complete a rigid structural frame. Midway of the opposite roof beams 30 is a longitudinal brace beam 36 aixed `at each end at 38 to the adjacent roof beam 30.

The largest structural element of each oscillator is its main inductor. In FIGURE 2 there are 6 such main inductors 40, 42, 4l4, 46, 48 and 50. These are for the 6 different octaves in the order of the reference characters given but they are not arranged geometrically in that order. Instead inductor 40 for the lowest octave, identiiied as octave 1 is at the top in FIGURE 4; inductor 42 "for octave 2' is'one position away from the bottom of the panel; inductor 44 for octave 3 is second from the top between octaves 1 and 5; inductor 46 for octave 4 is at the bottom and offset to one side below octave 2; inducwhich projects through the panel and out on the other outer side asV indicated at 56 in FIGURE 5. Each tube houses a ferro-magnetic core. Some of the cores are indicated at 58. Each core at its outer end has a pr0- jecting threaded brass stud 60 having threaded engagement with metallic cap 62 mounted on the end of the tube 56. By means of a screw `driver the stud 60 may be rotated to move the core 58 into various axial positions. The nature of the flux distribution is such that a material axial displacement of the core 58 produces a relatively slight change in the inductance of the inductor and thus it is easy for the assembler to adjust the inductance to tune the circuit. All the adjustment studs 60 project forwardly toward the serviceman when the panel 12 is removed, and each of them is labeled.

For instance, the panel illustrated in FIGURE 4 carries the indicia F# and the numbers 1, 2, 3, 4, 5 and 6 in the positions for the different octaves, so that the service operator can instantly identify any note and adjust its pitch immediately.

The particular space arrangement and the parallelism of all the cores 58 involves a rather critical allotment of available space, not from ra mechanical point of View but Vfrom a magnetic pointof view, in that if any of the inductors generates ya magnetic eld that strays over into the geometrical space occupied by the magnetic lield of an adjacent inductor, enough to Vaffect the oscillation of the adjacent oscillator, in frequency, or in amplitude, or

in wave shape, such magnetic leakage would interfere with the production of acceptable music.

When the finished musical tone is assembled from sine curve oscillations from a plurality of different oscillators, such -leakage from one magnetic lield into another is critical, but to apconsiderably lesser degree than when wave distortion is practiced. Many systems of tone building produce other wave shapes. If the sine curve .from the primary oscillator is changed to a different shape by Ya distorting device, such, kfor instance, as those disclosed in U.S. Patent 2,649,006, the distorting device will change the shape of the leakage vfrequency also, and this ywill generate the equivalent of oscillations with frequencies equal to the sum of the two original frequencies and, also equal to the dierence between the two frequencies.

VSuch random ghost frequencies are most objectionable,

and therefore better magnetic isolation for each eld is needed, to reduce the magnetic leakage.

`Accordingly it is emphasised that not one of the 6 induetors illustrated is adjacent another inductor that is only one octave removed in frequency. Considering, for instance, octaves 1 and 2, the octave of higher frequency has a field that occupies a smaller space volume and is three spaces away from octave 1. Similarly octave 2 is two spaces laway from octave 3 land both these octaves occupy a smaller space volume with their magnetic iields than octave 1, e

With respect to the entire assembly shown in FIGURE 1, each successive panel in the upper row is arranged with its lower octave at the top or lbottom and the -adjacent octaves on each side of it have their lower octave `at the lopposite end, adjacent octaves 4 and 6 of the lirst mentioned panel. Accordingly, up as far as octave S, every oscillator is abreast of oscillators in the adjacent chassis that are at least one octave removed and also of a diierent frequency. By Varranging all the panels in the uniform sequence of lthe chromatic scale with each octave one oscillator, one semi-tone lower than the octave 1 oscillator on the other side, interference between adjacent chassis is largely minimized. Another circumstance that makes minimum dimensions possible with the arrangement -disclosed .is that in ordinary music adjacent semivtones are almost never sounded because the simultaneous sounding yof `adjacent semistones is inharrnonic 'and musically distasteful. Therefore, octave 5, although it is abreast of other octave 5 oscillators differing from it by only one semi-tone pitch, is practically never sounded at the same time that one of the adjacent octave 5 oscillators is 4also being sounded. And Ian octave 5 oscillator a full semi-tone removed, which will often be sounded simultaneously, is separated by twice the horizontal Width of va complete chassis and completely outside the zone of possible interference.

Finally, the twelve chassis `are arranged in two rows of six, one above the other, and the relative vertical arrangement is with octave 1 oscillator of each chassis in the upper row adjacent oscillators `for octaves 4 and 6 in the `adjacent end of the chassis in the lower row. Another circumstance that contributes to the possibility of using the close spacing disclosed is that if oscillator 3 in FIG- URE 4 is oscillating with maximum amplitude :and 1% v of that oscillation is'transferred into oscillator 1 by the magnetic coupling, the oscillation in 'oscillator 1 will go into the same lin-al output cable with the oscillation from oscillator 3 and neither Ythe loud speaker-nor the `listener vtor for each oscillator.

at 68. Two conductors are vsoldered to tap 64. Conducf tor 70 leads up to the cooperating tank capacitor 72 and conductor 74 goes to the printed circuit. The remaining taps 66 and 68 are each connected to one conductor only. These three electrical contacts for each inductor winding are soldered by hand in the process of mass production. All of the terminals of all of the other components of all 6 oscillators extend physically to and through the printed circuit 34. In the particular embodiment rhsclosed additional control connections for each of `the oscillators are also mounted on the same printed circuit board although they do not constitute parts of the oscillator proper. These additional parts are two diodes 76 for each of the oscillators except octave 1. Octave l at the left end of FIGURE 3 has only one diode 76 mounted on the panel board and the circuit is completed by substituting a short piece of conductor `'78 where the other diode might be mounted. There is a 'similar diode in the assembled electrical conductor of which conductor 78 forms a part, 'but it is more convenient to mount it elsewhere.

VAll 6 transistors 80 are electrically connected by three terminals to the printed panel 34 and mechanically supported by the panel without any other mechanical support. The smaller 'capacitors and resistors for each oscillator are all mounted on the printed circuit 34, as clearly indicated in FIGURE 3, and mechanically supported entirely by the printed circuit.

Referring now to FIGURE 6, the terminal `84 comes from one of the larger and heavier components and it is expedient to give it a good mechanical connection to the printed circuit, The tubular stud 86 has its outer end slotted at 88 to define resilient'ngers 90 which, in undistorted condition, do not leave quite enough clearance tovpermit the tip 92 of the terminal 84 to pass through them. By thrusting this tip into the position shown in FIGURE 6 a frictional grip is secured to hold the terminal in position until the soldering has been done. The conductive area on the outer face of the printed circuit is indicated at 94. It will be obvious that inverting the stud from the lposition shown in FIGURE 6 and dipping it in solder will cause it to pick up a cap of solder indicated in dotted lines at 96 and thus the area and the stud and the terminal are all fused together into complete and permanent electrical connection.

For smaller and lighter components such as the resistor 96 of FIGURE 7-, it is sufficient to turn the terminals themselves at right angles as indicated at 98 and thrust the terminals up and through the appropriate conducting area of the panel. Subsequent dipping will form a cap at 100 performing the same function as the cap at 96.

The soldering process is a simple dipping operation. In FIGURE 5 I have indicated the chassis in the position where the printed circuit is inverted above a bath of molten solder at 102 preparatory to the soldering operation.

The terminals connected together by the printed circuit include an input conductor Yand an output conduc- The output conductors are all placed in parallel relationship and twisted together in an output cable at 104 (see FIGURE 2) and the input conductors are united in a similar cable 106. It is expedient to lead both twisted cables through a holding clip at 108, at the center of the longitudinal base bar 36 and to arrange the individual conductors in diverging relationship from there over to the printed circuit. It

will be obvious that each of the cables can be provided with a terminal plug 110 and that these terminal plugs can be plugged into receiving plugs in the proper relationship to the other components of the complete organ. If any serious defect is encountered in any one of the 6 oscillators, it is a simple matter to pull the plugs 110 and loosen the mechanical fastenings at 20 and replace that chassis with a duplicate chassis and send the chassis with a defective oscillator in it back to the factory.

Moreover, because all the chassis are geometrical duplicates with respect to the orientation of the printed circuit 34 and the #l inductor 40, positioning the inductors 40 alternately at the top and bottom arranges the printed circuits as indicated in FIGURE 8, in pairs facing toward each other. Between each pair ofprinted circuits, the open exposed sides of the frames are opposite each other to provide maximum clearance and enable a serviceman to reach in and touch any part suspected of a mechanical defect before removing one of the chassis. Also, the caps 96 and 100 protrude above the printed circuit in a pattern with which the serviceman is familiar, for convenient electrical testing for short circuits or open circuits. This provides maximum facility in locating a defect in what would otherwise be a very complicated procedure.

ln FlGURE 1l l have indicated an alternate form of inductor coil. The panel 16 is identical with that of FIG- URE 4. The winding 112 is devoid of the end plates 114 of FIGURE 2 and is affixed to the panel by an epoxy adhesive, with a slight excess of the adhesive extruded at 116. lt is orginally Wound on the tube 118 between temporary end plates, and is of wire carrying an insulating coating of synthetic plastic, which includes athermoplastic outer shell. Then the outer surfaces of the coil are lightly brushed with Van organic solvent to get the plastic in the outer turns a little softer, and the entirety is gently heated just enough to soften the plastic a little and weld all the turns to each other. This can be done in an oven, but a more convenient way is to generate the heat in the wire itself by passing current through itfor a short time. The caps 62 may be identical with caps 62 in FiGURE 5. At the other end, tube 118 is continued a little beyond the endV of the vwinding to support three terminals 120, which project axially beyond the end of the tube. These correspond to terminals 64, 66, and 68 in FGURE 2, and all three terminals can be soldered into their electrical assembly with the taps 122 from the coil, and the conductors to other components, in a single dipping operation.

Others may readily adapt the invention for use under various conditions of service by employing one or more of the novel features disclosed or equivalents thereof. As at present advised with respect to the apparent scope of my invention, I desire to claim the following subject matter: Y

1. In an electronic organ, in combination: a series of oscillators, one for each semi-tone of the musical scale within the range of the instrument; each oscillator including a tuned tank circuit having an individual inductor and individual meansfor precision adjustment of said inductor for tuning purposes; said oscillators being physically interconnected into a pluralityV of groups; each group comprising a plurality of octavely related oscillators; each group having apanel supporting the inductors of the group side by side in parallelism; each group having a frame supported by said panel and extending away from said panel .on one side only; a printed circuit sheet for each group; said sheet being mounted on` said frame, spaced from said panel, and with one face facing toward said panel and an opposite face facing away from said panel; a printed circuit on the face of said sheet remote from said panel; said oscillators having additional components, including triodes, resistors and capacitors; said frame, panel and sheet defining a compact, partially opening housing; the components for all the oscillators being substantially within the contines of said housing; said precision adjustments for said inductors being located accessibly on the outer face of the panel remote from said frame; certain other components being mounted on the inner face of said printed circuit sheet; said last mentioned components having terminal conductors passing through said sheet into electrical contact with said printed circuit; said terminal conductors having portions proiecting beyond said printed circuit; and solder electrically connecting and mechanically fastening all said projecting portions to said printed circuit.

2. In an electronic organ, in combination: a series of oscillators, one for each semi-tone ofthe musical scale within the range of the instrument; said oscillators being physically interconnected into a plurality of groups; each group comprising a plurality of oscillators; each oscillator having an inductor; each group of oscillators lhaving a panel supporting the inductors of the group side by side in parallelism; each group having a frame supported by said panel; a printed circuit sheet for each group; said sheet being mounted on said frame, spaced from said panel, and with one face facing toward said panel and an opposite face facing away from said panel; a printed circuit on the face of said sheet'remote from said panel; said oscillators having additional components, including triodes, resistors and capacitors; said frame, panel, and sheet delining a compact, partially open housing; the components for all the oscillators being substantially within the contines of said housing; certain of said components being mounted on the inner face of said printed circuit sheet; said last mentioned components having terminal conductors passing through said sheet into electrical contact with said printed circuit; said terminal conductors having portions projecting beyond said printed circuit; and means electrically connecting and mechanically fastening all said projecting portions to said printed circuit.

3. A combination according to claim 2 in which said `printed circuit sheet is set at a diagonal angle with one edge further from said panel than the other; whereby components mounted on the inner face of said printed circuit sheet are laterally accessible for removal and replacement.

References Cited in the tile of this patent UNITED STATES PATENTS 2,051,012 Schaper Aug. l1, 1936 2,223,539 Baker -Dec. 3, 1940 2,291,787 Beanland et al Aug. 4, 1942 2,495,339 Markowitz Jan. 24, 1950 2,555,039 Bissonette May 29, 1951 2,581,165 Bonanno Jan. 1, 1952 2,584,723 Mackey Feb. 5, 1952 2,588,082 Brown et al Mar. 4, 1952 2,603,774 Gusdorf et al. July 15, 1952 2,630,560 Earl et al. Mar. 3, 1953 2,728,054 Albers-Schoenberg Dec. 20, 1955 2,818,759 Peterson Jan. 7, -8 2,895,366 Schneeberger et al. July 21, 1959 2,924,784 Peterson Feb. 9, 1960 

